fix: canonical URLs to always include locale prefix

Fixed Canonical Redirect Error in Google Search Console by ensuring
canonical URLs always include the locale prefix (/sr, /en, /de, /fr)
instead of omitting it for the default locale.

Changes:
- layout.tsx: Fixed canonical and hreflang URL generation
- page.tsx: Fixed homepage canonical URL
- contact/page.tsx: Fixed contact page canonical URL
- about/page.tsx: Fixed about page canonical URL
- products/page.tsx: Fixed products page canonical URL
- products/[slug]/page.tsx: Fixed product detail canonical URL

Before: /contact (when locale=sr)
After: /sr/contact (all locales)

Fixes: Canonical Redirect Error in Google Search Console

src/app/[locale]/about/page.tsx

@@ -19,7 +19,7 @@ export async function generateMetadata({ params }: AboutPageProps): Promise<Meta
   const metadata = getPageMetadata(validLocale as Locale);
   const keywords = getPageKeywords(validLocale as Locale, 'about');
   
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${validLocale}`;
+  const localePrefix = `/${validLocale}`;
   const canonicalUrl = `${baseUrl}${localePrefix}/about`;
   
   return {

src/app/[locale]/contact/page.tsx

@@ -16,7 +16,7 @@ export async function generateMetadata({ params }: ContactPageProps): Promise<Me
   const metadata = getPageMetadata(validLocale as Locale);
   const keywords = getPageKeywords(validLocale as Locale, 'contact');
   
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${validLocale}`;
+  const localePrefix = `/${validLocale}`;
   const canonicalUrl = `${baseUrl}${localePrefix}/contact`;
   
   return {

src/app/[locale]/layout.tsx

@@ -21,11 +21,11 @@ export async function generateMetadata({
 }): Promise<Metadata> {
   const { locale } = await params;
   const validLocale = isValidLocale(locale) ? locale : DEFAULT_LOCALE;
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${locale}`;
+  const localePrefix = `/${locale}`;
 
   const languages: Record<string, string> = {};
   for (const loc of SUPPORTED_LOCALES) {
-    const prefix = loc === DEFAULT_LOCALE ? "" : `/${loc}`;
+    const prefix = `/${loc}`;
     languages[loc] = `${baseUrl}${prefix}`;
   }
 

src/app/[locale]/page.tsx

@@ -29,8 +29,8 @@ export async function generateMetadata({ params }: { params: Promise<{ locale: s
   setRequestLocale(validLocale);
   
   // Build canonical URL
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${validLocale}`;
-  const canonicalUrl = `${baseUrl}${localePrefix || '/'}`;
+  const localePrefix = `/${validLocale}`;
+  const canonicalUrl = `${baseUrl}${localePrefix}`;
   
   return {
     title: metadata.home.title,

src/app/[locale]/products/[slug]/page.tsx

@@ -57,7 +57,7 @@ export async function generateMetadata({ params }: ProductPageProps): Promise<Me
   const secondaryKeywords = keywords.secondary.map(replaceTemplate);
   
   // Build canonical URL
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${validLocale}`;
+  const localePrefix = `/${validLocale}`;
   const canonicalUrl = `${baseUrl}${localePrefix}/products/${slug}`;
   
   // Get product image for OpenGraph

src/app/[locale]/products/page.tsx

@@ -24,7 +24,7 @@ export async function generateMetadata({ params }: ProductsPageProps): Promise<M
   const keywords = getPageKeywords(validLocale as Locale, 'products');
   
   // Build canonical URL
-  const localePrefix = validLocale === DEFAULT_LOCALE ? "" : `/${validLocale}`;
+  const localePrefix = `/${validLocale}`;
   const canonicalUrl = `${baseUrl}${localePrefix}/products`;
   
   return {